Would asterisk work on something like this?
projectblackdog.com/site/index.html
Perhaps we could have an open source plug’n’play asterisk box then…
have you seen that blackdog is ? it’s completely host dependant, so you rely on the NIC of your USB-connected host for network, the hub/usb port for power, host IO for IO etc etc.
PSTN connectivity might be an issue too 
i can see some great possibilities, but imo, asterisk isn’t one of them.